E: unable to mount '/system'

Hi!
I have Mate 7 L09 (2gb of ram). Before i had lollipop 5.1.1 (b312) on my phone. Everything was ok, but i remembered that before on kitkat i had some "ios" animation pack installed and it was ok.
So from custom recovery, i installed that pack. (big mistake, don't do it) my phone started by i doesn't work properly. I had access only to settings. After that i did a wipe and a factory reset.
And from here my phone didn't want to boot. I only see the huawei logo. I tried to install the transition pack (by pressing vol - + vol + power) after many attempts i installed the pack. When i wanted to install the kitkat it froze at 90%. I did another wipe, another factory reset. And from here i tried a lot of combination. Lollipop bootloader, with kikkat installer, lollipop bootloader with update pack for lollipop, with transition pack. I tried also with kikkat bootloader and all the combination from above. When i install a custom twrp it tells me that i don't have any operation system on my phone.
I saw that i can't access system partition. When i want to wipe system partition it gives this error: E: unable to mount '/system'
What should i do?
Can you help me?

Thank you!